A fundamental of meditation is the ability to allow the body to deeply relax. Obviously if the position we are meditating in soon becomes uncomfortable or painful for the body, such relaxation will be harder to develop.
Drug abuse drastically changes the brain for the worse. Addiction hijacks pleasure centers, creates ingrained behavioral patterns, and kills brain cells. The good news is you can restore the brain after addiction.
If you spend time outside in spring, summer or early fall, sooner or later you will pick up ticks in their various stages or get bitten by flies or mosquitos, all of which can carry a range of different microbes. Several of these are associated with Lyme disease.